Thank you for stating what everyone should know.
Wi-Fi, Bluetooth, GPS - They don't take ANY significant amount of power unless you are actively using them. Don't bother turning them off and on - that likely takes more power than you would use.
As far as 8 hours - that's not bad if your using it alot. Why not buy a dock and put it in the dock when it's not actively being used.
ALWAYS turn GPS off. Nobody has any clue when what is used when with an Android device. perhaps some background app is using something. I always turn off GPS, WiFi (stops searching for access points on the road) and radio (same) when not using the items.
If I could say safely they weren't being used, I wouldn't turn them off but I definitely get better battery life turning them off.
SSHGuru is right. No need to turn GPS off. You can tell that GPS isn't being used when you don't want it to be.... no GPS icon in the notification bar = no GPS being used. Simple.
And pyro, do you just use the stock battery indicator? Ever actually tested your battery status/output with an outside app? I ask because 80% battery left after 16.5 hours, even with little usage, does not sound right. I know I've heard of people having problems with their stock battery status (and market apps too actually) misreporting what % life they had left. If you really are getting that kind of battery life, you must have one ideal setup workin for you.
Oh and to the OP, what does your phone say is using the battery? (menu > settings > about phone > battery use)